The question asks for the definition of Environmental Chemistry. We need to evaluate each option against the standard definition of this scientific discipline.
Correct Option: B) The branch of chemistry that deals with the origin, transport, reactions, effects and fates of chemical species in the environment (air, water, soil, living organisms).
This definition accurately encompasses all key aspects of environmental chemistry. It involves understanding natural chemical cycles, the impact of pollutants, and the chemical processes that govern the composition of air, water, soil, and living systems.
The question asks for the definition of an environmental pollutant. We need to identify the option that provides the most comprehensive and accurate definition, covering both natural and man-made sources and the impact on living beings and ecosystems.
Correct Option: B) Any substance present in the environment in an amount that is harmful to living beings or causes imbalance in the ecosystem, whether natural or man-made
The question asks to identify the atmospheric layer that extends from the Earth's surface to approximately 10 km altitude. This requires knowledge of the different layers of the atmosphere and their respective altitude ranges and characteristics.
Correct Option: C) Troposphere — the lowest layer where all weather phenomena and most air pollution occur; temperature decreases with altitude at ~6.5°C/km (lapse rate)
The question asks about the most important chemical feature of the stratosphere. We need to recall the characteristics of different atmospheric layers and the chemical processes occurring within them.
Correct Option: B) The OZONE LAYER (at ~20–30 km altitude) which absorbs harmful UV radiation (especially UV-B and UV-C) from the Sun, protecting life on Earth. This is the defining chemical characteristic of the stratosphere and is crucial for sustaining life on Earth by shielding it from damaging solar radiation.
The question asks why dinitrogen (Nâ‚‚) and dioxygen (Oâ‚‚) do not react under normal atmospheric conditions despite being major constituents. We need to evaluate the given options based on chemical principles.
Correct Option: D) Both N₂ and O₂ have very high bond energies (N≡N = 945 kJ/mol; O=O = 499 kJ/mol) — the activation energy for their reaction is extremely high, so they don't react at normal atmospheric temperatures. This option correctly identifies the high bond energies and the resulting high activation energy as the primary reason for their non-reactivity under normal conditions.
The question asks to identify the primary gaseous air pollutants in the troposphere. We need to distinguish between primary and secondary pollutants and identify the common gaseous pollutants directly emitted into the atmosphere.
B) Oxides of sulphur (SO₂, SO₃), oxides of nitrogen (NO, NO₂), oxides of carbon (CO, CO₂), hydrocarbons and hydrogen sulphide (H₂S) are all primary gaseous air pollutants. They are directly released into the atmosphere from natural or anthropogenic sources.